What is Embryo Freezing? Embryos can be frozen for up to five years, although this can be extended to ten years in exceptional circumstances. A frozen embryo transfer can be carried out on a natural cycle where patients do not need to take medications. In some circumstances, like irregular cycles or anovulation, a medicated (HRT) cycle is recommended, where drugs are used to prepare the endometrium for implantation. Pregnancy rates following frozen embryo transfer are generally lower than transfer of fresh embryos but, of course, it is much easier to undertake a frozen embryo transfer. There is now a large amount of accumulated data on outcomes of frozen embryo transfers, and there appears to be no increased incidence of fetal abnormalities associated with this procedure. It is estimated that about 90% of all frozen embryos survive the thawing process.
Who can benefit from Embryo Freezing? If the couple wish it, embryos that are not transferred to the uterus may be suitable for freezing. It is recommended that freezing is only undertaken if the embryos reach blastocyst stage and are of good quality. Implantation potential for blastocyst is very high, therefore even a single blastocyst can be frozen. We don’t recommend freezing embryos of poor quality, or those which develop slowly, as they are unlikely to survive the freezing and thawing process. It is important that you are aware that there is always a possibility that a low proportion or even none of the eggs fertilise. If this occurs you will be seen by the clinician to discuss your future options.
Before freezing Embryos HFEA regulations require that before embryos can be frozen, the couple need to give written consent to storage and their future use. Consent forms should be completed as accurately as possible as any inconsistencies in the couple’s consent forms may render the storage of the embryos invalid. The couple should notify the centre with any changes in address, contact details or to their circumstances.